Here's Featurefilmcasting.com's page back in October 2012...
On that same page, they also list CATWS casting for shoots beginning on March 1, 2013. Anthony Mackie just told AICN that they would start shooting on April 1; so if featurefilmcasting.com has a margin of error of +/- one month, I'd say their info on Ant-Man is pretty solid.
Here's where latinoreview got scoopage that Ant-Man is supposed to "step into Marvel's London production branch once principal photography on 'Thor: The Dark World wraps.'"
And that came hot on the heels of Simon Pegg tweeting about World's End finishing up and Ant-Man shooting in 2013.
And yes, all this came before Marvel gave Ant-Man the late 2015 release date, but as of yet, there's no indication that Wright has changed his plans for Ant-Man at all. Maybe we'll hear something from the horse's mouth soon one way or the other, but otherwise, there's more solid evidence that Ant-Man *is* shooting soon than there is evidence against that. Feel free to provide linkage to prove me wrong, though.